The present invention relates to a surface-mount type electrolytic capacitor and a method of producing the same. In particular, the present invention relates to a surface-mount type electrolytic capacitor exhibiting improved reliability and a method of producing the same.
A conventional surface-mount type electrolytic capacitor is disclosed in, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2006-128247 (hereafter referred to as Patent Document 1). The surface-mount type electrolytic capacitor disclosed in Patent Document 1 is called a three-terminal transmission-line element. As disclosed in Patent Document 1, the surface-mount type electrolytic capacitor uses an electrically conductive functional polymer film as a solid electrolyte. The surface-mount type electrolytic capacitor comprises a plurality of capacitor elements. In order to produce each capacitor element, an anodized coating layer is at first formed on a surface of a valve-action metal, so that a valve-action metal anode is prepared. Then, the electrically conductive functional polymer film is formed so as to cover the center portion of the anodized coating layer surface of the anode. A graphite layer is formed around the electrically conductive functional polymer film. Furthermore, a silver paste layer is formed as a cathode layer. After the above-mentioned layers are formed in this order, an anode lead portion at an end portion of the capacitor element is connected, by the use of an electrically conductive adhesive, through an electrically conductive spacer to an anode terminal formed in a resin case. A cathode portion at a center portion of the capacitor element is connected, by the use of an electrically conductive adhesive, directly to a cathode terminal formed in the resin case. Thereafter, an exterior case cover is fixed with an adhesive.
In the conventional surface-mount type electrolytic capacitor, the capacitor element is placed in the resin case, and is connected and fixed to the anode and cathode terminals. Thereafter, the exterior case cover is fixed to the resin case, and sealing is performed. In each of the fixing operations, an electrically conductive adhesive or an adhesive is used and subjected to drying and curing. Therefore, a fixing jig and a drying furnace are required for each of the fixing operations. An apparatus and a lead time in the production process are required for each of the drying and the curing steps. Furthermore, in joining the resin case and the exterior case cover, nonuniformity or variation may occur in distribution of the adhesive, resulting in nonuniformity or variation in adhesion or residual strain. As a consequence, characteristics tend to vary and uniform quality is not obtained.